Metal stencil



Aug. 1s, 1931. y G F nog 1,819,927

' METAL STENCIL Filed Aug. l, 1929 Fig. I.

CARBIJLUY -6 Inventor: George Taylor2 His Attrorneg.

Patented ug. I8, 1931 UNITED STATES PATENT OFFICE GEORGE E. TAYLOR, oFsCHENECTAbY, NEW YORK, AssIGNoE 'ro GENERAL ELECTRIC COMPANY, ACORPORATION OF -NEW YORK METAL s'rENCIL Application led August 1, 1929.Serial No. 382,707.

The present invention relates to metal stencils made from-hard,wear-resistant ma-v terialand vto a method for making them. Ordinarily,metal stencils are constructed of relatively soft metals.` Such stencilsare obviously not suitable for use when abrasive materials are employedin the stenciling operation, for example in stencilling an insignia onglass by means of sand blast apparatus.

It is one of the objects of the present invention to provide a metalstencil. which is very hard an'd tough and capable of practicallyunlimited wear without serious de- 1s terioration even when used inconnection with sand blast a paratus.

The material which I employ in the construction of my improved stencilis a sintered composition consisting of tungsten carao bide and cobalt.A metallic composition of this character'is disclosed in the patents toSchrter Nos. v1,549,615 and 1,721,416, and, in general, contains from afew percent to about cobalt, the remainder of the composition beintungsten carbide.

The novel eatures which are characteristic of my invention are set forthwith particularity in theb appended claims. My invention itself howeverAwill best be understood from reference to the following specicationwhen considered in connection with the accom anying drawings in whichFigs. 1, 2, 3 an a are'views representing various steps in the formationof the stencil; Fig. 5 is a perspective view of an application of mfyimproved stencil 5 Fig. 6 is a plan view ol a glass' plate .whlch asbeen stencilled with my improved stencil, while Fig. 7 illustrates amodification. of my invention.

In carrying out my invention, Ivymix v.tungsten carbide and cobalt inpowdered form in the proportion ofabout 13% cobalt and 87% tungstencarbide with a smallamount of starch aste, and spreadthe powderedmixture 1 etween two molybdenum lates 2 and 3, each about '116' to 1/8thick. e plates 2 and 3v and interposed mixture 1 are then laced in aclosed' carbon'receptacle (not s own) and the'mixture slightly 'sinteredby firing at a. temperature of about ing or bending of the plate 5formed in t e process.

s 850 to 950 C. .for about 72hours in a hydrogen atmosphere. During. thesintering operation a small weight 4 is applied to the mixed powderedmaterial to prevent warV The slightly sintered plate 5 is dat and may behandled easily without breaking. It isalso relatively soft and may beeasily worked or cut by sand blast apparatus.

To cut an insignia in plate 5, it is laced under avsuitable stencil 6and a san blast 7 directed against the plate and the superimposedstencil, as indicated in Fig. 3. The plate is relatively soft and thesand blast easily cuts through it. After the insignia has been cut,plate 5 is again placed between molybdenum plates 2 an'd 3 and weight lagain ap lied thereto. The combined plates and weig t are thenplaced inla closed carbon boat and heated 1n a hydrogen furnace to a temperaturewhich may vary from about 1375 to 1400 C. which is the sinteringtemperature' of the mixed materials. When. heated to this temperature,plate 5 becomes'very hard and tough and wear-resisting and may beemploye lwith a sand blast apparatus to stencil a glass plate 8.

The weight employed in pressing the powdered materials 1 or thepartially sintered plate 5 should not be .too heavy as otherwise themolybdenum plates 2 and 3 will stick to the intermediate plate when itis heated to the temperature em. loyed. It will be found that a weightof a ew pounds per square inch will Vprovide sucient pressure to'preventthe plate 5 from warping during t e heating process. v

Instead of employing the metall stencil 6, I may cover the partiallysinteredplate 5 ce with a layer 9 of wax, cut the desired impression inthe wax so as vto ex Ose portions A of the plate 5, and appl a san blastto the mixture oftuiigsten carbide and'oolmlt,l it lwill be obvious thatother sntered hard 100 perature of about 1350 metal compositions may beemployed if desired. For example, molybdenum carbide may be substitutedfor tungsten carbide, while nickel or iron or any combination ofV iron,nickel and cobalt up to 25% of the total content of the composition maybe employed. v

A higher percentage of cobalt' than 2570 may be employed if desired. Itshould benoted however that as the cobalt content of the compositionisincreasedthe sintered late 5 becomes softer. Likewise, as the coaltcontent decreases, the composition becomes very hard and at the sametime quite brittle.

What Iclaim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. The method of making a stencil from a mixture of powdered materialswhich comprises forming the powdered materials into a substantially flatplate, partially sintering the plate at a relatively low tempera.-V turewhile under pressure, cutting an insignia in the plate and heating theplate under pressure to a relatively high temperature.

2. The method of making a stencil from a mixture 'of powdered materialswhich comprises binding the powdered materials together under pressureat a relatively low temperature to form a plate, perforating the late toproduce an insignia therein and heating the plate under pressure to arelatively l high temperature.

3. The method of making a stencil from a mixture of powdered materialsconsisting largely of tungsten but containing appreci- -able amounts ofcobalt and carbon, which comprises forming the powdered materials into asubstantially flat plate, heating the..

powdered materials under pressure to a tema?, f2

perature varying from about 850 C. to about 950. C.,perforating theplate and again heating the plate under iressure to a tem- In witnesswhereof, I have hereunto vset my hand this 31st day of July, 1929.

GEORGE F. TAYLOR.

